MICROSCOPIC DESCRIPTION: The sections show fragments of bronchial mucosa, bronchial wall including cartilage and muscle. Two fragments show infiltrative tumour composed of irregular cords and nests of cells with hyperchromatic nuclei, and with focal unambiguous squamous differentiation including single dyskeratotic cells, intercellular bridges and abundant eosinophilic cytoplasm. Mitotic figures and apoptoses are frequent. There is ulceration and necrosis.